Member
Joined 2002
Curently i have these people down for boards if i missed yuo please let me know.
Brian Donegan 2 boards
Cambe 2 board
IlyaMK2 boards
mlloyd1 4 boards
jason
Brian Donegan 2 boards
Cambe 2 board
IlyaMK2 boards
mlloyd1 4 boards
jason
Mind if i ask if the 6 device boards are made the same way/quality as the
10 device version ?
If so, then i am in for 2 boards.
(not for my personal diy sillyness though, my plate is full !
)
J.
10 device version ?
If so, then i am in for 2 boards.
(not for my personal diy sillyness though, my plate is full !
)J.
The layout is similar, but only for 3 output devises.
If enough are interrested I might go forward with an order.
I'll have to see what the prices are for a 2.4 mm board with 3 oz CU.
\Jens
If enough are interrested I might go forward with an order.
I'll have to see what the prices are for a 2.4 mm board with 3 oz CU.
\Jens
I'd go for the 6 device version. 10 seems a bit excessive (for me), but 4 might be too puny (in plastic). Like a mini-Leach (mini-L?).
Depends what you intend it for, Bill.
You should take a look at the Leach manual Jens made.
Remember that practically all those plastics can do 30 amps for 10 milliseconds with voltage over collector and emitter up till 30 volts.
With 3 parallel devices thats 90 amps.
PS voltage at say 55 vdc means 3 parallel plastic dudes can deliver their full 6*150watts max into a 1 Ohm load within soa.
(for 150 watt devices)
With normal loudspeakers nowadays, as the awfull Apogee's are a goner, 1 ohm impedances occur only in the upper frequency range with ribbon tweeters.
Dont think you need regular lights anymore if you pump 900 watts in them.
In the low frequencies regular loudspeakers do not go to low impedance behavior.
With 55vdc at continuous full power 3 parallel sets could do 650 watts, if the ps can keep delivering that.
I dont see those who go for smaller Leach boards equip the amplifiers with 650 watt powersupplies for continuous abuse.
4 device boards are not Puny at all.
6-device boards would make it killer amps though with ps voltage below 55vdc.
You should take a look at the Leach manual Jens made.
Remember that practically all those plastics can do 30 amps for 10 milliseconds with voltage over collector and emitter up till 30 volts.
With 3 parallel devices thats 90 amps.
PS voltage at say 55 vdc means 3 parallel plastic dudes can deliver their full 6*150watts max into a 1 Ohm load within soa.
(for 150 watt devices)
With normal loudspeakers nowadays, as the awfull Apogee's are a goner, 1 ohm impedances occur only in the upper frequency range with ribbon tweeters.
Dont think you need regular lights anymore if you pump 900 watts in them.
In the low frequencies regular loudspeakers do not go to low impedance behavior.
With 55vdc at continuous full power 3 parallel sets could do 650 watts, if the ps can keep delivering that.
I dont see those who go for smaller Leach boards equip the amplifiers with 650 watt powersupplies for continuous abuse.
4 device boards are not Puny at all.
6-device boards would make it killer amps though with ps voltage below 55vdc.
Jacco,
I'll make some calculations on the railvoltage for the 6 transistor version. I think it will be ok to drive the thing at 60V rails into 4 ohms. Not sure though, I'll post some graphs later tonight or tomorrow.
J time 🙂
\Jens
I'll make some calculations on the railvoltage for the 6 transistor version. I think it will be ok to drive the thing at 60V rails into 4 ohms. Not sure though, I'll post some graphs later tonight or tomorrow.
J time 🙂
\Jens
Hi Jacco-
Ok, I was being a little sarcastic. I, afterall, have Klipsch horns, which are very efficient. I am building the Aleph30 for those. Not actually sure why I need to have 6-7 amplifiers anyway, but what the heck. They are fun to build.
BTW: It's Brian, not Bill 😉
Ok, I was being a little sarcastic. I, afterall, have Klipsch horns, which are very efficient. I am building the Aleph30 for those. Not actually sure why I need to have 6-7 amplifiers anyway, but what the heck. They are fun to build.
BTW: It's Brian, not Bill 😉
Hey, you are talking to a retard here !
I'll keep saying sorry till the next millenium, Brian.
Sorry, Mr Brian D.
I am in for the 6 device boards too, the 4's i'd skip but not because they are Puny.
A lot of designs were puny, they needed fast protection circuitry to prevent the output from frying to death.
Even many DIY designs, 150 watt amplifiers running on 4 150 watt devices.
Which is silly, considering the cost of 2 extra power transistors per channel.
Big news:
My IRFP240's are in, i will be entering Aleph territory again soon !
(Mmm, after i built the Mosfet A40's with Mike's boards which i promised to him)
I am sure why: because i am a nut as Casey says !!
I'll keep saying sorry till the next millenium, Brian.
Sorry, Mr Brian D.
I am in for the 6 device boards too, the 4's i'd skip but not because they are Puny.
A lot of designs were puny, they needed fast protection circuitry to prevent the output from frying to death.
Even many DIY designs, 150 watt amplifiers running on 4 150 watt devices.
Which is silly, considering the cost of 2 extra power transistors per channel.
Big news:
My IRFP240's are in, i will be entering Aleph territory again soon !
(Mmm, after i built the Mosfet A40's with Mike's boards which i promised to him)
I am sure why: because i am a nut as Casey says !!
Hello to everyone, can I ask for 2 or more boards (depending on the price) ???? I prefer the 4 devices version but I'll get what you decide...
I am interested in the 6 device boards when you get the price figured out. I'm having an awful time with these Superamp boards.
Do you think it will work OK on 64v rails? I have some spare Hafler transformers.
Blessings, Terry
Do you think it will work OK on 64v rails? I have some spare Hafler transformers.
Blessings, Terry
Rails
Terry,
The railvoltage depends on the load that the amp will see.
If you have 8 ohm speakers you should be ok with 64V rails.
I will have to check when I get home what the recommended rails are.
Jacco may have an answer - Jacco?
\Jens
Terry,
The railvoltage depends on the load that the amp will see.
If you have 8 ohm speakers you should be ok with 64V rails.
I will have to check when I get home what the recommended rails are.
Jacco may have an answer - Jacco?
\Jens
I'll post some graphs later tonight or tomorrow.
Hi Jens, in post 67 you wrote:I'll post some graphs later tonight or tomorrow
Do you have some pictures allready for the 6 transistor version?
Thanks, Loek
Hi Jens, in post 67 you wrote:I'll post some graphs later tonight or tomorrow
Do you have some pictures allready for the 6 transistor version?
Thanks, Loek
If you take a look at output stages of commercial amplifiers the common thing is a total power capability of the output devices of around 4 times the rms rating in 8 Ohms.
If 150 watt devices are used total power would be 900 watts for the 6 device Leach.
The above would indicate a 225 watts in 8 Ohms amplifier.
I suppose you are meaning 45Vac transformers, around 64 Vdc, Terry ?
If you are using a single transformer for the voltage and current stage, not like me a higher voltage for the front end by using a step-up transformer, the net voltage on the output is below 60 Volts.
On top of that voltage will drop significantly into lower impedance loads, depending on size of the transformer and the capacitor number.
Suppose 55Vdc into 4 Ohms, which is 110 Vpp.
Jens graphs for the Leach manual alreay showed for a number of devices that a Vce of 100 Volts is a critical point.
The non-derated soa curve does about 1 Amp at 100 Vce.
At 10 Volts output, non-derated that would be safe for 3.3 Ohms with 3 devices.
If you go lower than 4 Ohms ps voltage will drop even further, non-derated a six-device output can deliver much more current safely.
If you derate the soa area for higher temperatures than 25C for the Die this would not be sufficient.
A thing to keep in mind is that SOA is measured for a single non-repetitive burst.
Regular music signals are sine waves.
A sine wave has an average of 2/3.14 of the value of a constant signal (Integral [Sinx] from 0 to Pi/2)
Average power of a sine wave is even lower.
Power is square(voltage) divided impedance.
If voltage is not constant but has a Sine shape average power is 1/2 of the value for a constant voltage
( Integral square[Sinx] from 0 to Pi/2 )
Now if you use NORMAL loudspeakers the impedance will not drop below 3 Ohms in the lower frequency range.
Loudspeakers with ribbon tweeters have a impedance dip in the higher range.
But those signals are very short, and average power handling capability of a ribbon tweeter is low.
Non-derated the soa of an MJL1302 does 1 Amp at 100Vce, for 100-250 mS.
However, for a 10 mS signal it is more like 3 Amps per device.
For a 1 mS signal max current is 15 Amps or higher.
A 10 mS burst of 1 Amp at 100 Vce is 100 watts for 10 mS.
But that is only 1 Joule (watts is Joules/sec), equivalent with 1 watt continuous over 1 second.
Because it is a Sine wave in reality it is only half, so 1/2 watt based on 1 second.
(Integral square[Sinx] = 1/2 !! )
On top of that an output device is working half of the time, the other half it is resting and cooling down.
So 1 Amp for 100 Vce during 10 mS Sine waves translates to 25 watts dissipation for a 50 Hz Sine tone.
A number of people have posted on different threads to derate soa curves to 50 % (Die temperature = 87,50 C ).
A 20 Hz tone has a half Sine duration of 25 mS, at 50 % soa derating the 3 device Leach is easily capable of operation in 3 Ohms impedance.
At 50 Hz, half Sine is 10 mS. 50 % derating leads to 1,5 Amp per device.
Times 3 = 4,5 Amps, which is safe for impedances higher than 2,2.
And undoubtebly under 2 Ohms, because voltage will drop far below 55 Vdc.
Above 500 Hz(half Sine = 1 mS) , the current capability is 7,5 Amps per device at 50% derating.
22,5 Amps for 3 devices, and at 10 Volts output that drives impedances even lower than 0,5 Ohms.
In reality if you use regular loudspeakers, and are not running a disco, temperature of the device Die's will be much lower than 87,50 C.
I would use a decent heatsink on the 6 device Leach, a figure of 0,30 C/W, a thermal protection and/or a current protection circuit with an output relay.
I'll skip the phase shift part.
Long story, my simple opinion : 64 volts works.
btw: my network at home is out of Bizz untill wednesday, i am likely not to read diy stuff every day.
The Nut.
If 150 watt devices are used total power would be 900 watts for the 6 device Leach.
The above would indicate a 225 watts in 8 Ohms amplifier.
I suppose you are meaning 45Vac transformers, around 64 Vdc, Terry ?
If you are using a single transformer for the voltage and current stage, not like me a higher voltage for the front end by using a step-up transformer, the net voltage on the output is below 60 Volts.
On top of that voltage will drop significantly into lower impedance loads, depending on size of the transformer and the capacitor number.
Suppose 55Vdc into 4 Ohms, which is 110 Vpp.
Jens graphs for the Leach manual alreay showed for a number of devices that a Vce of 100 Volts is a critical point.
The non-derated soa curve does about 1 Amp at 100 Vce.
At 10 Volts output, non-derated that would be safe for 3.3 Ohms with 3 devices.
If you go lower than 4 Ohms ps voltage will drop even further, non-derated a six-device output can deliver much more current safely.
If you derate the soa area for higher temperatures than 25C for the Die this would not be sufficient.
A thing to keep in mind is that SOA is measured for a single non-repetitive burst.
Regular music signals are sine waves.
A sine wave has an average of 2/3.14 of the value of a constant signal (Integral [Sinx] from 0 to Pi/2)
Average power of a sine wave is even lower.
Power is square(voltage) divided impedance.
If voltage is not constant but has a Sine shape average power is 1/2 of the value for a constant voltage
( Integral square[Sinx] from 0 to Pi/2 )
Now if you use NORMAL loudspeakers the impedance will not drop below 3 Ohms in the lower frequency range.
Loudspeakers with ribbon tweeters have a impedance dip in the higher range.
But those signals are very short, and average power handling capability of a ribbon tweeter is low.
Non-derated the soa of an MJL1302 does 1 Amp at 100Vce, for 100-250 mS.
However, for a 10 mS signal it is more like 3 Amps per device.
For a 1 mS signal max current is 15 Amps or higher.
A 10 mS burst of 1 Amp at 100 Vce is 100 watts for 10 mS.
But that is only 1 Joule (watts is Joules/sec), equivalent with 1 watt continuous over 1 second.
Because it is a Sine wave in reality it is only half, so 1/2 watt based on 1 second.
(Integral square[Sinx] = 1/2 !! )
On top of that an output device is working half of the time, the other half it is resting and cooling down.
So 1 Amp for 100 Vce during 10 mS Sine waves translates to 25 watts dissipation for a 50 Hz Sine tone.
A number of people have posted on different threads to derate soa curves to 50 % (Die temperature = 87,50 C ).
A 20 Hz tone has a half Sine duration of 25 mS, at 50 % soa derating the 3 device Leach is easily capable of operation in 3 Ohms impedance.
At 50 Hz, half Sine is 10 mS. 50 % derating leads to 1,5 Amp per device.
Times 3 = 4,5 Amps, which is safe for impedances higher than 2,2.
And undoubtebly under 2 Ohms, because voltage will drop far below 55 Vdc.
Above 500 Hz(half Sine = 1 mS) , the current capability is 7,5 Amps per device at 50% derating.
22,5 Amps for 3 devices, and at 10 Volts output that drives impedances even lower than 0,5 Ohms.
In reality if you use regular loudspeakers, and are not running a disco, temperature of the device Die's will be much lower than 87,50 C.
I would use a decent heatsink on the 6 device Leach, a figure of 0,30 C/W, a thermal protection and/or a current protection circuit with an output relay.
I'll skip the phase shift part.
Long story, my simple opinion : 64 volts works.
btw: my network at home is out of Bizz untill wednesday, i am likely not to read diy stuff every day.
The Nut.
Hi jacco,
Thanks for all the info. Some of it got through this thick skull. 😀
One thing in particular that you mentioned is of interest to me. The Hafler transformer that I have was designed for the XL280. It has three secondary circuits. One is 70VDC for running the front end, one is 64VDC for the output MOSFETs, and then there is a 15VDC circuit. This tranny might be perfect for doing what you are talking about. What do you think? By the way it is an EI core.
Is the board that Jens designing for this capable of running the two voltages? Can it be split so the driver portion runs at a different voltage thant the outputs?
Thanks, Terry
Thanks for all the info. Some of it got through this thick skull. 😀
One thing in particular that you mentioned is of interest to me. The Hafler transformer that I have was designed for the XL280. It has three secondary circuits. One is 70VDC for running the front end, one is 64VDC for the output MOSFETs, and then there is a 15VDC circuit. This tranny might be perfect for doing what you are talking about. What do you think? By the way it is an EI core.
Is the board that Jens designing for this capable of running the two voltages? Can it be split so the driver portion runs at a different voltage thant the outputs?
Thanks, Terry
Terry,
why need i answer if you do it yourself ?
I gathered Jens planned to use for the small Leach basically the same Layout as his extended Leach design.
Which has PS-feeding to the front stage through an RC-filter tapped from the board fuses exit.
For twin power leads the RC-filter is skipped, the higher voltage line soldered in the secondary pad of the resistor.
With 70 Vdc secondaries you have plenty voltage to drive the output to its full potential on 64 Vdc, you could even add regulators.
The 15 Vdc secondaries are great for protection circuitry.
But you already figured that.
Besides a much higher power output you end up with an amplifier that is even more stable by using multiple separated powerlines. Because the PS for the current amplification does not influence the PS for the voltage gain.
Hope your Super Leach works out in the end, Terry, you invested a lot of effort.
why need i answer if you do it yourself ?
I gathered Jens planned to use for the small Leach basically the same Layout as his extended Leach design.
Which has PS-feeding to the front stage through an RC-filter tapped from the board fuses exit.
For twin power leads the RC-filter is skipped, the higher voltage line soldered in the secondary pad of the resistor.
With 70 Vdc secondaries you have plenty voltage to drive the output to its full potential on 64 Vdc, you could even add regulators.
The 15 Vdc secondaries are great for protection circuitry.
But you already figured that.
Besides a much higher power output you end up with an amplifier that is even more stable by using multiple separated powerlines. Because the PS for the current amplification does not influence the PS for the voltage gain.
Hope your Super Leach works out in the end, Terry, you invested a lot of effort.
Uh, I don't understand that comment. Maybe this thick head. 😀
This is good news. Do you think the 6 outputs will handle the voltage OK?
I am having a heck of a time getting it right. For some stupid reason I installed the wrong value resistors in a few places. I've got those all squared away now but it plays very distorted.
I'm not seeing any voltage drop across R46 and R48. Also, adjusting P1 does nothing that I can see. I'm telling you, there is something to be said for silk-screen. I think I'll stick to premade PCBs for a time until I get a better grasp on things.
Your right, I've spent a lot of Time, effort and cash. I sure hope I can get this figured out. I had high hopes for this amp.
Blessings, Terry
The way i see a transistor is as a resistor with a variable resistance depending on the voltage at the base.
In that sense the power capability depends on the temperature of the transistor, which gives a margin till the transistor core reaches the breakdown temperature.
Its resistance determines the voltage drop from collector to emitter, Vce.
A high resistance means high Vce, a high current through a high resistance means high dissipation, means higher core temperature.
Both parameters too high and max temperature is exceeded and the transistor dies.
Now if you keep the temperature of the transistor low, the device can handle more heat for certain time periods before it fries.
And if the current going through it does this for a short period of time, the transistor is able too cool down before it is thermally attacked again.
That is why transistors handle more current for shorter periods at the same Vce value(resistor value).
If the interval is twice as short the current can be higher because at the end of the time interval the transistor die can cool down again.
So, if you stay at a safe temperature for the transistors by cooling them decently with proper heatsinks and assume they will stay below the 50% temperature SOA line they will live if at any frequency currents are not too high for a certain interval.
That currents do not exceed the limit for certain durations is what i've shown in the previous posting by expressing frequencies in time intervals, and checking how high currents can be for a certain voltage drop over the transistors collector to emitter.
The Leach amplifier has a built-in current limiting circuit that reduces voltage level to the driver stage if the output current exceeds the maximum acceptable.
Under normal operation parameters a 6 device Leach can handle a 64 Vdc PS easily.
A lot better than a number of commercial amplifiers from the past, i could give you a number of examples.
I posted a picture of a protection circuit some time ago, that compares output voltage and output current.
If a combination of high Vce and high current exceeds the level that is acceptable the circuit triggers a relay to shut the output down.
imo, any BJT amplifier output stage can be killed, i would never use one without protection.
Unless you desire to build an amplifier that is able to drive the worst loudspeaker under tropical conditions, but then you are thinking of the old Thresholds, and the K-brand.
If you use a normal loudspeaker on the small Leach the amplifier has plenty reserves with 6 output devices.
Use horrible low impedance monsters and you should look at other designs with much higher device numbers.
I am building the Leach with 10 because it will drive Quad ESL's, which has a 2.4 Ohms impedance at low frequency level.
A 6 device Leach with such high voltage would be suicide on those loudspeakers.
If i cant get the vented heat tunnels cool enough to go deep in class A i'll add another 10 Toshiba 1302/3281.
But the Leach amplifier for me is a nice project to see how much i can tweak out of it with different settings, different devices and biased heavilly.
In that sense the power capability depends on the temperature of the transistor, which gives a margin till the transistor core reaches the breakdown temperature.
Its resistance determines the voltage drop from collector to emitter, Vce.
A high resistance means high Vce, a high current through a high resistance means high dissipation, means higher core temperature.
Both parameters too high and max temperature is exceeded and the transistor dies.
Now if you keep the temperature of the transistor low, the device can handle more heat for certain time periods before it fries.
And if the current going through it does this for a short period of time, the transistor is able too cool down before it is thermally attacked again.
That is why transistors handle more current for shorter periods at the same Vce value(resistor value).
If the interval is twice as short the current can be higher because at the end of the time interval the transistor die can cool down again.
So, if you stay at a safe temperature for the transistors by cooling them decently with proper heatsinks and assume they will stay below the 50% temperature SOA line they will live if at any frequency currents are not too high for a certain interval.
That currents do not exceed the limit for certain durations is what i've shown in the previous posting by expressing frequencies in time intervals, and checking how high currents can be for a certain voltage drop over the transistors collector to emitter.
The Leach amplifier has a built-in current limiting circuit that reduces voltage level to the driver stage if the output current exceeds the maximum acceptable.
Under normal operation parameters a 6 device Leach can handle a 64 Vdc PS easily.
A lot better than a number of commercial amplifiers from the past, i could give you a number of examples.
I posted a picture of a protection circuit some time ago, that compares output voltage and output current.
If a combination of high Vce and high current exceeds the level that is acceptable the circuit triggers a relay to shut the output down.
imo, any BJT amplifier output stage can be killed, i would never use one without protection.
Unless you desire to build an amplifier that is able to drive the worst loudspeaker under tropical conditions, but then you are thinking of the old Thresholds, and the K-brand.
If you use a normal loudspeaker on the small Leach the amplifier has plenty reserves with 6 output devices.
Use horrible low impedance monsters and you should look at other designs with much higher device numbers.
I am building the Leach with 10 because it will drive Quad ESL's, which has a 2.4 Ohms impedance at low frequency level.
A 6 device Leach with such high voltage would be suicide on those loudspeakers.
If i cant get the vented heat tunnels cool enough to go deep in class A i'll add another 10 Toshiba 1302/3281.
But the Leach amplifier for me is a nice project to see how much i can tweak out of it with different settings, different devices and biased heavilly.
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